Osulf I (Oswulf) (d.963) was earl of Bernicia from 930 and of all Northumbria from 954 until his death. He is known mostly for conspiring to with Earl Maccus, son of Olaf Guthfrithson or Olaf Sihtricson, to kill Eric Bloodaxe, king of York. After Eric's death, Edred, king of England, gave the once Norse-held lands south of the river Tees to Osulf, who was already in possession of Bernicia north of the Tees.